The present invention relates generally to wafer probe alignment, and more specifically, to a method, wafer probe alignment system and a computer program product, for aligning a probe to a chip wafer for testing a chip on the wafer.
Wafer testing is a step performed in wafer fabrication and test laboratories using a wafer probe. All chips on a wafer may be tested for functional defects and performance data by applying special test patterns. A probe card or test board with microscopic contacts is installed to the wafer probe while the wafer is held, for example, by vacuum on a chuck and moved into the contacts to established electrical contact between the chip and the test system via the test head.
During test, it is necessary to have electrical contacts for all test signals, and appropriate power connection is required to ensure realistic test results. This requires planarity between test board contacts and the wafer. To assure planarity, a grid of signal pins may be adjusted to the chuck, and thus the wafer surface, by adjusting the top plate of the wafer probe. The test board may also be adjusted to have planarity between the electrical contacts and the test board mechanic. The contacts of the test board may include no moving parts. In this case, planarity is essential. In other cases, the test board may be mounted with some flexibility allowing auto-micro-adjustments.
During wafer test, the chuck moves the wafer into the contact to establish electrical contacts, which requires a certain force depending of the number of contacts. This force may cause mechanical distortion of the wafer probe and top plate of the wafer probe, which may impact the planarity between wafer probe contacts and the wafer and may lead to contact loss of one or several signals, potentially worsening power connections, which could influence the test results. To correct planarity between the wafer and probe contacts, during contacting of the chip on the wafer an adjustment mechanic may be inserted to a top plate of the wafer probe. This adjustment mechanic may be operated, e.g., manually.